starr



(No Model.)

' E. T. STARR.

RHBOSTAT.

No. 266,911. Patented 0013.31, 1882.

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UNITED STATES PATENT OFFICE.

ELI T. STARR, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR OF @NE-HALE TO WILLIAM J. PEYTON, OF WASHINGTON, D. U.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 266,911, dated October 81, 1832.

Application filed August '25, 1882. (No model.) Patented in England July 13, 1882, No. 3,330.

To all whom it may concern Be it known that I, ELI T. STARR, ot' the city and county of Philadelphia, in the Slate ot' Pennsylvania, have invented certain new and useful Improvements in Rheostats or Ptesistance Devices for Electric Circuits, ot' which the following is a specification, my said improvements having been patented in England July 13, 1882, as No. 3,330.

1o My invention relates to variable-resistance devices for electric circuit-s for governing more especially the action of electro-magnetic motors employed for driving light inachinerysuch as sewing-machines, lathes, tbc-whereby the speed and powerofthemachine or machines being` driven by the motor may be readily controlled by the operator.

The object of my present invention is to provide an improved variable-resistance circuit- 2o controlling device which is simple, inexpensive, and very eiiicient.

The subject-matter claimed is particularly pointed out at the close ot' the specification.

Some ot' my improvements may be used wi thout the others; and my improvements may ot' course be used with electric circuits not including electric motors wherever applicable.

In the accompanying drawings, which illustrate lny present improvements as embodied 3o in the best way now known to me, Figure lis a plan or top dew ot' my improved variableresistance device organized for use with a pivoted treadle, and Fig. 2 is a side elevation thereof.4 Fig. 3 is a side elevation ofthe variable-resistance device organized for use with a detent or stop arrangement, whereby the resistance may be determined by adjustment, andthe device then Xed so as to maintain the resistance as adjusted.

4o A base or stand, A, is provided with bimling-screws t a i'or connecting the ends of the circuit-wires 1 2, which lead to and t'rom a battery or other generatorot" electricity, which circuit may include an electro-magnetic motor or motors when such is or are to be used. Said binding-screws are in electrical connection by wires 4, respectively, with the variable-resistance device, so as to constitute said device apart ot' the electric circuit. Said variableresistance device consists of a coil, B-prcferably a spring-coil-ol'ering comparatively high resistance to the passage of the current when in its normal condition, and the resistance of the circuit is determined or varied by expanding or contract-ing the members of' said coil, as 55 will hereinafter appear. Said resistance-coil is preferably made in the tapering or conical form shown in the drawings, with the member of the coil ot' largestdiameter next the baseboard A, upon which the coil may be mounted, 6o and the successive members of the coil gradually lesseuing in diameter to the apex or upper end of' the coil, whereby upon pressure heilig applied to the smaller end ot' said coil to compact it its members will be compressed and be brought into surface contactfrom the larger to the smaller end ot' the coil in regular order, the members of the resistance-coil, in other words, gradually closing from its larger end to its smaller end, and thereby short-circuiting 7o the current across the members ot' the coil, as will be obvious, instead ot' compelling itto traverse the coil in a spiral direction from end to end, as will be the case when the coil is in its normal condition of full expansion.

The wire 3, for instance, is connected with one end ot' thc coil, while the wire 4, in such case, is connected with the opposite end of the coil. The upper end ot' the coil, in the organization shown in Figs, 1 und 2, is connected 8o with the toe otI an insulated treadle, C, pivoted to the base-board A, the toot of the operator being placed upon said treadle to compact the coil by downward pressure,so as to vary the resistance otlered by the working-circuit to the S5 passage ot' the current, and thereby, as will be obvious, affecting the action ct'the electric motor should one be included in the circuit. By removing' the pressure the coil immediately expands, so as to offer the maximum resistance, 9o the spring at the same time returning the treadle or lever to its normal position; or the return of the treadle may be ei'i'ected by a separate or auxiliary spring, c, acting upon the treadle imlependently ot' the coil. 95

Vhen my improved resistance device is used to govern the actiouot' an electric motor the maximum resistance ot" the coil should be sut'- licient to permit the passage through the circuit of a current ol" just sufficient strength to roc drive the motor and machine ope ated thereby at a comparatively slow rate of speed. Vhen greater speed and power are required, downward pressure of the foot may be employed to throw out a part of the resistance, more or less7 as required, so that the motor, and consequently the machine driven by it, may readily be driven at the required speed. When the resistance-coil is completely compacted or depressed the minimum resistance only is offered to the current, and the speed and power of the machine will consequently be at its maximum, and the extent of this range of resistance to be thrown in or cutout of the circuit will ofcourse be determined to suit the particular circumstances under which it is required to work.

It will thus be seen that I have produced a resistance-coil for electric circuits which may be compressed by force in one direction to lessen its resistance gradually and to any desired extent, and by its own action or resilience return to its normal position to interpose its maximum resistance when the pressure is removed, this operation taking place without at'- fecting the continuity ot' the current. This I believe to be anew and highly useful, while very simple, form of resistance device for electric circuits.

It will ot course be understood that the expansible and contractible variable-resistance coil may be made in other forms than the tapering form shown, while preserving its novel characteristics. For example, the members of the coil may be made of substantially the same diameter throughout,but of different power as respects their capacity to resist compression, whereby upon the application ot' pressure to compact the coil its respective members will close gradually and in regular order. In some cases, also, the coil, instead of having the spring capacityinitself,may bemade so as to be thrown outward after compression by a separate spring-for instance, an insulated spring inclosed by the coil. In some cases, also, the resistance-coil, with its members adapted to close gradually and in order to short-circuit the current across them, may lack the spring capacity, and be compressed and expanded positively, in order to vary the resistance of an electric circuit.

I preferin some instances to guide the resistance-coil in the expansion and contraction of itsmembers-as, for instance, by inserting` within the coil a guide, b, on which an insulating ring or button, b', is fitted to slide freely, and iit the toe end of the treadle C thereto, so as to bear upon said ring` by a slotted connection, (clearly shown in Fig. 1,) which connection between the treadle and coil is a sliding or yielding one. Such an organization ot' parts insures the proper working and gradual orderly closing of the members of the coil, and avoids any rocking of said members relatively to each other, or lateral movement of said resistance-coil upon its base, due to the vibration of the treadle on its hinge or pivot.

In Fig. 3 I have shown my improved coil as a spring-coil, with the central guide, b, and

say that I am aware that resistance-coils forming part ot' an electric circuit have been suggested in order to vary the resistance of the circuit by bringing more or less of the members of the coil into surface contact by pressure; butin such cases there is no provision for preventing several members ot' the coil from coming into contact at the same instant, and consequently the coils are defective in that a gradual resistance or closing of the members of the coil in succession or order one after another is not attained. By constructing the coil in a tapering form (or with its members of gradually-decreasing diameter) or in equivalent ways a greatly superior coil is obtained, and one which permits the resistance of an electric circuit to be graduated or varied to a nice or slight degree.

I claim herein as of my inventionl. The improved variable-resistance coil for electric circuits, constructed, substantially as hereinbefore set forth, of a tapering or equivalent form, whereby the respective members ot' the coil close in contact with each other gradually and in order one after another when subjected to pressure.

2. The combination, substantially as hereinbefore set forth, with an electric circuit, of a variable-resistance coil the members of which are constructed in a tapering or equivalent way, so as to close gradually and in order under pressure to short-circuitthe current.

3. The combination, substantially as hereinbet'ore set forth, ot' an electric circuit, a resistance-coil the members of which are constructed ina tapering or equivalent way, so as to close gradually and in order under pressure to short-circuit the current, and mechanism to compact said coil.

4. The combination, substantially as hereinbefore set forth, with an electric circuit, of a spring resistance-coil constructed in a taper'- ing form or equivalent way, so that its members close in order under pressure, and mechanism to compact said coil and permitit to return to its normal condition by its resiliency when the pressure is removed.

In testimony whereof I have hereunto suhscribed my name this 19th day of July, A. l). 1882.

ELI T. STARR.

Witnesses:

WM. J. lnv'roN, E. EUGENE STARR.

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